Browne's resignation is effective Monday. Also stepping down is Joseph Salgado, a principal deputy director at the lab.

In an interview, Browne said he felt his credibility had suffered too much to be able to guide the lab through the latest round of problems.

"The controversy was so strong and so critical of management that I personally thought the best thing for me to do was resign and to have the university come in and take it to the next level of performance," he said.

The Energy Department, the FBI and at least two congressional committees are investigating allegations of credit card abuses at the lab over the past several years and the disappearance of high-tech hardware and other equipment.